Difference between MIMO and Spatial Multiplexing

MIMO and spatial multiplexing are two inter-related concepts often used interchangeably in mobile communications. MIMO or Multiple Input Multiple Output is an antenna technology first introduced in the 3G UMTS networks as part of HSPA enhancement. Modern mobile networks, including both 4G LTE and 5G NR, use different variants of MIMO technology to improve signal quality and network capacity. LTE is capable of providing average data speeds in tens of Mbps. Have a look at our dedicated post that shows the achievable average download and upload speeds with 4G LTE and LTE Advanced networks. Together with technologies like carrier aggregation, MIMO plays a key role in enabling high data rates in 4G LTE networks. Furthermore, an enhanced version of MIMO, Massive MIMO, is used by 5G New Radio (NR) networks to improve 5G network capacity.

MIMO is an advanced antenna technology that improves the radio signal link quality and data rates by employing multiple transmitter and receiver antennas; spatial multiplexing is a technique that enables improved data rates in MIMO by transmitting and receiving multiple streams of the overall data.

Spatial multiplexing enables higher data rates in MIMO

Spatial multiplexing is also referred to as Space Division Multiplexing (SDM), and it is one of the critical building blocks for MIMO in 4G LTE and 5G NR networks. Spatial multiplexing relies on various antennas that are separated physically in space by their angular direction. These spatially separated antennas can send and receive multiple data streams in parallel through the same block of frequency and time resources. Through numerous antennas at both the transmitter and the receiver, MIMO can benefit from spatial multiplexing by using each data stream as a separate channel. That increases the available network capacity for the transmitter and the receiver. When the individual data streams arrive at the receiver, they are combined to create the output data, which results in improved data rates for the mobile user.

MIMO uses spatial multiplexing for higher throughput

MIMO- Multiple Input Multiple Output uses spatial multiplexing to improve data rates for mobile users. Spatial multiplexing is the primary reason for the inclusion of MIMO in 4G LTE and 5G NR networks. In addition to spatial multiplexing, MIMO also benefits from two other capabilities, spatial diversity and beamforming, which improve the signal quality and the network range. The original LTE networks had a MIMO configuration of 4×4 in the downlink (network to the phone) and 2×2 in the uplink (phone to the network). A configuration of 4×4 means four antenna elements at the transmitter side and four antenna elements at the receiver. The configuration increased to 8×8 in the downlink and 4×4 in the uplink in LTE-Advanced and LTE-Advanced Pro networks. 5G NR networks employ an enhanced version of MIMO called Massive MIMO, which has tens of antenna elements at the transmitter and the receiver. Massive MIMO also utilises the multi-user MIMO capability, which increases the network capacity in 5G networks.

Conclusion

MIMO is an antenna technology that improves the radio signal quality and data rates by using multiple antennas at the transmitter and the receiver. Spatial Multiplexing is an enabler for MIMO technology. It allows the antenna elements in the transmitter to send multiple data streams carrying bits and pieces of the overall data in parallel to the user device. As a result, spatial Multiplexing enables data rate improvement for MIMO systems.

Here are some helpful downloads

Thank you for reading this post, I hope it helped you in developing a better understanding of cellular networks. Sometimes, we need some extra support, especially when preparing for a new job, studying a new topic, or maybe just buying a new phone. Whatever you are trying to do, here are some downloads that can help you:

Students & fresh graduates: If you are just starting, the complexity of the cellular industry can be a bit overwhelming. But don’t worry, I have created this FREE ebook so you can familiarise yourself with the basics like 3G, 4G etc. As a next step, check out the latest edition of the same ebook with more details on 4G & 5G networks with diagrams. You can then read Mobile Networks Made Easy, which explains the network nodes, e.g., BTS, MSC, GGSN etc.

Professionals: If you are an experienced professional but new to mobile communications, it may seem hard to compete with someone who has a decade of experience in the cellular industry. But not everyone who works in this industry is always up to date on the bigger picture and the challenges considering how quickly the industry evolves. The bigger picture comes from experience, which is why I’ve carefully put together a few slides to get you started in no time. So if you work in sales, marketing, product, project or any other area of business where you need a high-level view, Introduction to Mobile Communications can give you a quick start. Also, here are some templates to help you prepare your own slides on the product overview and product roadmap.

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